Curing Kinetics Analysis of Dgeba-Mda System

Thermoset polymers and thermoset based composites are normally polymerized and performed in a step process. This work studies the kinetics behavior of a commercial epoxy system used as matrices of medium and high performance composite materials. The characterization study was performed by differential scanning calorimetry (DSC) and spectroscopic analysis

Furfuryl Alcohol-Based Resin as Matrix for High Performance Composites:

The polymerisation of a furfuryl alcohol-based resin, used as matrix for glass-fiber-reinforced composite materials, was studied by differential scanning calorimetry (DSC), and an empirical kinetic model of the complex reactive process was developed. The kinetic investigation led to the determination of kinetic constants, activation energies, and reaction orders for the adopted kinetic model

Preparation and Characterization of Nanocomposite Films

The incorporation of nanosized inorganic particles into a polymeric matrix represents the most important problem in the nanocomposite fabrication. Success in manufacturing materials for optical devices can be achived only if the particle aggregation is avoided. This paper describes the preparation of a polymeric nanocomposite containing a well-dispersed red pigment synthesized using nanosized titania particles

A Method for Simple and Precise Measurements of Kinetics of Reactions between SiC and Molten Al

Reinforced aluminum is generally fabricated by liquid metal infiltration. The reinforcement degradation produced by molten matrix is the major problem to be considered. The relationship between conversion and thermal exposure time is an important information. In the present paper a method for measuring the conversion by weight determinations is proposed

Wettability of Copper Coated Carbon Fibers

The wetting kinetics of a solid surface by a molten metal decrease with increase of its roughness. The topography of the growing copper coating, produced on carbon fiber surface by electroplating from a sulphat bath, has been studied by scanning electron microscopy. The smoothes surface is produced after 200÷300 milliampere-hour of plating

Wear effects in retrieved acetabular UHMW-PE cups

There is an increasing awareness of the clinical problems associated with ultra-high-molecular-weight polyethylene (UHMW-PE) wear and failure in orthopaedics. This disadvantage is certainly promoted from the various oxidation process that can occur during prosthesis life. Scanning electron microscopy, IR-spectroscopy, and X-ray-photoelectron spectroscopy were employed to investigate the mechanism of polymer degradation. In particular, comparison among the spectra of starting and retrieved UHMW-PE components shows that the polymer oxidizes mainly in vivo. The data indicate that hydroxyl radicals are likely to be a major factor in degradation of the surface of this polymer, these groups are produced in vivo during the implantation time. Several other chemical groups, produced in the different steps of the prosthesis life, are contained in the material

Photovoltaic Systems Reconfiguration

2013 - 2014A photovoltaic field is typically composed by series-connected panels, thus composing strings, which are then connected in parallel. By this way, the current and the voltage values of the photovoltaic generator are adapted to operating range of the power electronics systems that transform the generated energy, conveying it to the load and to the electrical grid. The performance of the photovoltaic systems are reduced when a partial shading of the field occurs. In this case, the modules could work under very different conditions from each other, so that the system components may not be able to maximize the generated energy and/or the operating constraints of power electronics systems are not respected. The reconfiguration of the electrical connections among the panels leads to maximize the performance of the photovoltaic systems but it requires additional hardware and it causes further energy consumptions that have to be minimized by executing the reconfiguration procedure only when the shading phenomena occur. The choice of the electrical configuration of the panels is determined by an appropriate algorithm and then it is actuated by a matrix of relays... [edited by author]XIII n.s

Nanocomposites Based on Metal and Metal Sulfide Clusters Embedded in Polystyrene

Transition-metal alkane-thiolates (i.e., organic salts with formula Me(SR)x, where R is a linear aliphatic hydrocarbon group, –CnH2n+1) undergo a thermolysis reaction at moderately low temperatures (close to 200 °C), which produces metal atoms or metal sulfide species and an organic by-product, disulfide (RSSR) or thioether (RSR) molecules, respectively. Alkane-thiolates are non-polar chemical compounds that dissolve in most techno-polymers and the resulting solid solutions can be annealed to generate polymer-embedded metal or metal sulfide clusters. Here, the preparation of silver and gold clusters embedded into amorphous polystyrene by thermolysis of a dodecyl-thiolate precursor is described in detail. However, this chemical approach is quite universal and a large variety of polymer-embedded metals or metal sulfides could be similarly prepared

Use and Abuse of Digital Devices: Influencing Factors of Child and Adolescent Neuropsychology

The impact of technology on human life is significant, touching various aspects such as communication, economy, education, medicine, industry, and even ecosystems [...]

Synthesis of gold nano-plates by mercaptide thermolysis in poly(vinyl acetate)

Triangular gold nano-plates have been synthesized by thermal decomposition of Au(I) dodecyl-mercaptide (i. e., AuSC12H25) dissolved in poly(vinyl acetate). Such special shape was achieved because of the ability of polymer side- groups (i. e., the acetate groups) to be selectively absorbed on the most acid faces of the growing gold nanocrystals, thus inhibiting crystal development along these crystallographic directions. Nano-plates had an average edge length of ca. 30 nm and a thickness of a few nanometers